1. Field of the Invention
The present invention relates to a drive system, and more precisely relates to a drive system, which is capable of moving travellers in the same direction at the same speed.
2. Description of Background Art
A conventional drive system, which is capable of moving travellers in the same direction at the same speed, is shown in FIG. 8.
The conventional drive system 200 has a pair of linear guides 202a and 202b, which are arranged parallel in a Y-direction. A pair of travellers 204a and 204b are capable of moving in the Y-direction along the linear guides 202a and 202b. A connecting member 206 is spanned between the travellers 204a and 204b to connect both together. A ball screw 208, which is arranged in the Y-direction, is screwed with the traveller 204a. The ball screw 208 is rotated by a motor 210.
In the drive system 200, the traveller 204a is moved in the Y-direction along the linear guide 202a when the motor 210 starts and the ball screw 208 is rotated. Since the travellers 204a and 204b are connected by the connecting member 206, which is made by a tough material such as a steel, the traveller 204b is moved together with the traveller 204a.
Tools or workpieces, for example, can be attached to the connecting member 206. The attached tools or workpieces can be moved in the Y-direction together with the connecting member 206.
However, the conventional drive system 200 has following disadvantages.
The traveller 204a is directly driven by the ball screw 208; the other traveller 204b is driven by the traveller 204a with the connecting member 206. Thus, the driving force applied to the traveller 204a is not equal to that applied to the traveller 204b. The traveller 204a begins to move before the traveller 204b when the motor 210 starts. By the time lag, the connecting member 206, which must be parallel to an X-axis for precise operation, inclines with respect to the X-axis, so that positioning accuracy of the tools or the workpieces, which have been attached to the connecting member 206 is decreased. Namely, it is impossible to precisely synchronize the parallel movement of the travellers 204a and 204b when the driving force applied to the travellers 204a and 204b is unbalanced, so that the precise positioning cannot be executed. Further, the same problem occurs when external force is applied to any movable sections.
To solve the problems, which are caused by the unbalanced driving force applied to the travellers 204a and 204b and the external force applied to the movable sections, a tougher and thicker connecting member 206 has been employed to reduce said starting time lag between the travellers 204a and 204b. But the movable sections must be heavier, so that high speed operation cannot be executed. Further, load of the motor 210 must be greater, so that a motor having greater torque must be required for the motor 210.